Method of surfacing solid bodies



Patented Mar. 10, 1953 METHOD OF SURFACING SOLID BODIES Georges H. J. Monnet, Moirans, France, assignor to Socit Anonyme des Manufactures des Glaces et Produits Chimiques de Saint-Gobain, Chauny & Cirey, Paris, France No Drawing. Application May 12, 1949, Serial No. 92,944. In France May 13, 1948 16 Claims.

The present invention has for its object a process for surfacing solid bodies by rubbing their surface by means of abrading or polishing blocks with an interposed liquid; it has more particularly for its object the surfacing of solid bodies having comparatively large surfaces such as for example plates or sheets and, especially, the obtaining of a fine smoothing and polishing of glass sheets.

The method according to the present invention consists in using rubbing blocks made of abrasive or polishing grains bonded by a material which is less hard, less abrasive or less polishing than the grains, and preferably has no abrasive or polishing properties, and in disaggregating the binding material by the action, controlled at will, of a physical or chemical agent, so as to uncover or disembed the abrasive or polishing grains along a part of their height.

Preferably the proportion of the binding material used for producing the rubbing block is such that the volume of said material be greater than the space constituted by the whole of the interstices which would exist between the grains If they were supposed to be in contact with one another. Such a proportion of the binding material permits to obtain that the active grains be separated from each other and act individually.

From that fact and as a result of the grains individually having their base embedded in the binding material, each grain penetrates into the surface to be worked along only a fraction of its height and consequently the work of the grains is finer than if they were freely acting 'under a rubbing block.

When and as the block works, it becomes less and less efiicient, as its rubbing surface wears out by itself. The method according to the present invention permits to reinstate the efficiency of the block by means of the action of an agent disaggregating the binding material so as to eliminate the superficial layer of the block which had become inactive, thus denuding the underlaying layer which remains active, in order to let it work in its turn.

For the so-called reviving operation formerly the work of the block was stopped and the superficial layer was removed by means of a hard tool or by abrasion. For the blocks which are the subject matter of the invention, the reviving operation is obtained by causing the disaggregating agent to act on the working surface of the block, either by interrupting the work of the block, or without stopping it and in this latter case, in a continuous or discontinuous way.

The disaggregating agent may act either chemically or physically, by dissolution or in any other way; its nature depends upon the composition of the binding material.

The association of the binding material with the disaggregating agent must be such that said agent itself or the products resulting from its action on the binding material will have no objectionable effect on the body to be surfaced nor on the work of the block.

The disaggregating of the binding material by chemical action is particularly suitable for cases where the solid material to be surfaced, glass for instance is not much liable to be affected by chemical attack; the disaggregating of the binding material by physical action is suitable for materials, metals for instance, liable to be affected by chemical attack.

According to a first embodiment of the invention, the block is constituted of abrasive grains agglomerated by means of a cement that may be decomposed by an acid, the disaggregating of the binding material being obtained by means of said acid.

According to a second embodiment of the invention, grains of an abrasive material such as quartz, emery, corundum, diamond, etc., or of a polishing material, such as rouge (iron sesquioxide), stannic-dioxide, alumina, etc., are agglomerated by means of a metal or a metallic alloy. The association of the metal with the disaggregating agent is so chosen, as aforesaid, that the disaggregation will have no objectionable effect on the surfaced body nor on the surfacing work. When the surfaced body is not or little liable to be affected by acids, there may be chosen a metal which may be decomposed by an acid constituting the disaggregating agent, for instance zinc and hydrochloric acid. If the body is affected by acids, the disaggregating agent may be a salt acting on the metal by double decomposition: for instance zinc will be associated with a ferric or stannic salt. If the surfaced body is not affected by bases, it is possible for instance to associate copper with ammonia as a disaggregating agent. By choosing a metal or an alloy Which may be decomposed by water, water may constitute the disaggregating agent.

In a general way, by a suitable association of the binding metal with the disaggregating agent, the block may be worked as is desired in an acid, neutral or basic medium, permitting to reach optima working conditions.

The agglomeration by means of a metal affords the advantage that if a fragment of the block 3 breaks off, there is less risk of it spoiling the surfaced body than when the agglomerating material is hard, of ceramic for instance, and the risk is the smaller as the metal is less hard.

A particular example of blocks where the binding material is a metallic one consists in constitutingthem by agglomerating abrasive or polishing grains with a powdered metal by compression and heating or by any other process suitable for agglomerating metallic powders.

According to another embodiment of the invention, the block may be constituted by a metallic alloy containing elements of dilferent hardnesses, generally crystallized, the less hard and less abrasive ones being the more easily attacked by a chemical agent which is the disaggregating agent. For instance there may be used a carbon steel thermally treated so that its structure will present cementite and ferrite; cementite is the abrasive element which is hard, not easily attackable, and ferrite is the less hard element more attackable by the disaggregating agent; such agent may be one of the reagents used in metallography to evidence the structure of steels.

Another way of carrying out the disaggregation by chemical action, which may be used when the abrasive block is a conductor of electricity, consists in attacking it by electrolysis, by passing a direct current through the rubbing surface so that the block will constitute the anode. The current may be fed either through the body to be surfaced if it is a conductor, or through the working liquid.

Another embodiment of the invention which is particularly suitable for surfacing bodies easily affected by chemical actions consists in constituting the rubbing block by agglomerating the abrasive or polishing grains with a gum, a natural resin or an artificial plastic material and in using as a disaggregating agent a solvent of such substances: alcohol, acetone, gasoline, etc.

The present invention has also for its object the application of the process according to the invention in the surfacing of glass articles which are to be polished, for obtaining the very fine smoothing preceding the polishing operation. The blocks are made of fine abrasive grains bonded by a material which may be disaggregated by a suitable agent. Glasses being, according to their composition, more or less liable to be affected by chemical action, the association of the binder with the disaggregating agent must be chosen so that disaggregation will not be objectionable either for the glass nor for the surfacing work. The binding material being for example a metal, it is possible, as above stated to obtain blocks which will be disaggregated as desired either in acid, neutral or basic medium.

The present invention has also for its object, the use of the process according to the invention for polishing glass. The blocks are made of grains of a polishing material agglomerated by means of binder which may be disaggregated by a suitable agent. The association of the binder with the disaggregating agent is chosen, as above said, so that disaggregation will take place in an acid, neutral or basic medium. The disaggregating of the binding material may take place while the work of the block is interrupted. But the disaggregating of the binder may also be accomplish-ed without causing the block to cease to remain in contact with the glass; there are thus avoided stoppages of the work, accidents and faults which may occur by the fact that the block does not bear on the glass over its whole surface when, after having been withdrawn for the disaggregating of the binding material, the block is again set in its place for resuming its work.

In any case, the abrading or polishing material, the binding substance and the disaggregating agent must be chosen according to the nature of the body to be surfaced and the kind of the surfacing work to be performed.

What is claimed is:

1. The method of grinding glass that includes the step of rubbing it with a zinc block containing a finely divided, uniformly dispersed abrasive, and flowing HCl into contact with the glass and block during the grinding.

2. The method of grinding glass that includes the step of rubbing it with a zinc block containing a finely divided, uniformly dispersed abrasive, and bringing a salt from the class of iron and tin salts between the faces of glass and block.

3. The method of grinding glass that cornprises grinding it with a copper block containing a dispersed abrasive in fine particles, and flowing ammonia between the engaged surfaces.

4. The method of grinding an acid resistant material that comprises grinding it with an abrasive block containing a finely divided inert abrasive set in an acid soluble binder, and flowing such acid between the block and material during grinding.

5. The method of grinding a base resisting material that comprises grinding it with an abrasive block containing a finely divided inert abrasive set in a base soluble binder, and flowing such base between the block and material during grinding.

6. The method of grinding a salt resistant material that comprises grinding it with an abrasive block containing a finely divided inert abrasive and a binder decomposable by a salt, and entering such salt between the block and material during grinding.

7. The method of grinding a conductive body that comprises connecting said body as cathode in an electrolytic circuit, grinding it with a conductive block containing a dispersed abrasive, connecting said block as anode in the electrolytic circuit, bringing an electrolyte between the bodies during grinding, and passing electrolytic current therethrough from the block as anode.

8. The method of surfacing a solid body such as glass that includes the step of rubbing said body with a block comprising a finely divided abrasive agglomerated with a binding material softer than the abrasive, said binding material occupying a volume greater than the space that would exist between the grains of abrasive if they were in contact with one another the grinding being performed in the presence of a liquid to which the body to be surfaced is resistant and which gradually disaggregates the binding material and uncovers a part of the height of the abrasive grains.

9..The method of surfacing a solid body such as glass that includes the step of rubbing said body with a block made of a finely divided abrasive held in a matrix of metal softer than said body, the metal being present in a volume greater than the space that would exist between the grains of abrasive if they were in contact with one another, in the presence of an acid to which the abrasive and the body to be surfaced are resistant and in which the metal dissolves, and thus gradually dissolving the metal and uncovering a part of the height of the abrasive grains.

10. The method of. surfacing a solid body such as glass that includes the step of rubbing said body with a block made of a finely divided abrasive held in a matrix of copper which is present in a volume greater than the space that would exist between the grains of abrasive if they were in contact with one another, the rubbing being performed in the presence of an acid in which the copper dissolves and to which the body to be surfaced and the abrasive are resistant, and which gradually dissolves the copper and uncovers a part of the height of the abrasive grains.

11. The method of surfacing a solid body such as glass that includes the step of rubbing said body with a block made of a finely divided abrasive held in a matrix of zinc and present in a volume greater than the space that would exist between the grains of abrasive if they were in contact with one another, the grinding being performed in the presence of an acid in which zinc dissolves and to which the body to be surfaced and the abrasive are resistant and which gradually dissolves the zinc and uncovers a part of the height of the abrasive grains.

12. The method of surfacing a solid body such as glass that includes the step of rubbing said body with a block made of a finely divided abrasive held in a matrix of metallic alloy which is present in a volume greater than the space that would exist between the grains of abrasive if they were in contact with one another, the grinding being performed in the presence of an acid in which the alloy is soluble and to which the body to be surfaced and the abrasive are resistant and which gradually dissolves the alloy and uncovers a part of the height of the abrasive grains.

13. The method of surfacing a solid body such as glass that includes the step of rubbing said body with a block made of a carbon steel containing cementite, constituting the abrading agent, and ferrite which is less hard than ce- -mentite and more liable to be attacked by an 14. The method of grinding glass that includes the step of rubbing it with a metal block containing a finely divided inert abrasive, and flowing into contact with the glass and the metal block during the grinding, an acid, inert to the glass and the abrasive, capable of reacting with the metal of the block to form a salt inert to the glass.

15. The method of surfacing a solid body that includes the step of rubbing said body with a block comprising a finely divided inert abrasive dispersed evenly throughout a solid binding material which is inferior to the abrasive in at least one of the properties of hardness, abrasiveness, and polishing ability, and inserting a dissolving agent for said binding material between the surfaces of said body and block during the surfacing operation in sufiicient quantity to uncover a part of the height of the abrasive grains.

16. The method of grinding a material reistant to electrolytes that comprises grinding such material with a block containing a dispersed inert abrasive set in a binder that is soluble in an electrically energized electrolyte, flowing an electrolyte between material and block, during the continuance of the grinding whenever it is desired to sharpen the block, and electrically energizing the electrolyte during the grinding.

GEORGES H. J. MONNET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

